Automatic shifting multi-speed power transmissions, especially three and four speed versions, have been used in passenger vehicles for some time. These transmissions have generally used two simple planetary gear sets or a single compound planetary gear set, such as those proposed by Ravigneaux. There have been five speed transmissions utilizing Ravigneaux speeds proposed for automotive transmissions also.
As a general rule, these arrangement produce two underdrive ratios, a direct drive ratio and an overdrive ratio. The five speed Ravigneaux set will produce two or three underdrive ratios, a direct ratio and two or one overdrive ratios depending upon the gear sizes selected and ratio steps desired.
Many of the three speed arrangements have been extended to four speed versions by adding a simple planetary, generally at the input, to provide an overdrive input ratio to the three speed transmission.
A desire for transmissions with five speeds has emerged, many of these transmissions are proposed with either three simple planetary gear sets or, as mentioned above, a Ravigneaux gear set which is compounded. The compounded Ravigneaux gear set includes two sun gears, two ring gears, the compound long/short pinion carrier assembly interconnecting each of the sun and ring gears. These Ravigneaux arrangements generally three concentric coaxial shaft/gear combinations which result in increased barrel diameter for the transmission case. In transverse from drive vehicles, the case size is not as critical as for longitudinal rear wheel drive vehicles.